Re­mains of a co­los­sal, sur­pris­ingly bird-like di­no­saur have been un­cov­ered in In­ner Mon­go­lia, Chi­na, sci­en­tists say.

The an­i­mal, which lived in the Late Cre­ta­ceous pe­ri­od, about 70 mil­lion years ago, is thought to have weighed about 1,400 kilo­grams (3,000 pounds). That’s sur­pris­ing, pa­le­on­tol­o­gists said, be­cause most the­o­ries sug­gest car­niv­o­rous di­no­saurs got smaller as they evolved to be­come more bird-like.

The di­no­saur, de­scribed in this week’s is­sue of the re­search jour­nal Na­ture, has been classed as a new spe­cies and ge­nus.

Artist's re­con­struc­tion of Gi­gan­torap­tor with much smaller feath­ered di­no­saurs known as or­ni­tho­mi­mids. (Cour­t­esy Zhao Chu­ang and Xin­g Li­da/IVPP)

Xin­g Xu of the Chin­ese Acad­e­my of Sci­ences in Bei­jing and col­leagues an­a­lyzed the ske­l­e­ton and grouped the fos­sil with a family that in­clud­ed the beaked, bird-like Ovi­rap­tor, be­cause of its si­m­i­larly avi­an fea­tures. The fa­mily is known as Ovi­rap­tor­o­sau­ria.

But what’s most strik­ing, the re­search­ers said, is that the beast was about 35 times heav­i­er than oth­er si­m­i­lar feath­ered di­no­saurs, which rarely ex­ceeded 40 kilo­grams. Al­so, the “bizarre” shape of cer­tain bones in­di­cates the an­i­mal, dubbed Gi­gan­torap­tor er­lia­nen­sis, was “a highly spe­cial­ized lin­eage,” Xu and col­leagues wrote.

The au­thors es­ti­mate that the new di­no­saur would have been about eight me­tres (26 feet) long and would have stood, at the shoul­der, twice the height of a ma­n. They sug­gest that a growth rate con­sid­erably faster than large North Amer­i­can tyran­nosaurs con­tri­but­ed to this. The team al­so no­ted lines of ar­rested growth on the fos­sil, in­di­cat­ing that it was still a young adult when it died. That sug­gests the full-sized di­no­saur may have been even larg­er, they argued.